[split] util-core: prefer Await.result(future.liftToTry) to deprecated methods

Problem

It is not obvious to clients what the preferred mechanism is for
getting back the result of a `Future` as a `Try`.

Solution

Add documentation to `Await` that leads people to use a non-deprecated
approach of `Await.result(future.liftToTry)`.

Update existing code to use this mechanism as well to avoid the
deprecated `Future.get(Duration)` call.

Result

Less usage of deprecated code, better docs and make this
approach more obvious for future coders.

RB_ID=463483
[split] util, ostrich, finagle, twitter-server: Remove all trailing spaces

Problem

Trailing spaces are not recommended in our code style.
It generates noise during code reviews, because most people configured their
editor to automatically remove them.

Solution

Bulk remove of the spaces with sed, below the command line used:
for dir in util ostrich finagle twitter-server; do
  find $dir -type f -name '*.scala' -or -name '*.java' -exec sed -i "" "s/[[:space:]]*$//" {} \+
done

Result

All next code reviews will be exempt of noise.

RB_ID=463585
TBR=true
[split] util: Fix the Travis CI

Problem

Travis CI is currently failing on util, apparently because the travis file is not well written.

Solution

Fix the Travis CI definition.

RB_ID=465585